In a spacecraft, a thruster is installed to control a posture. The thruster generally includes an iridium catalyst charged in an engine and hydrazine as a propellant. The thruster provides momentum by ejecting a gas generated by degradation of hydrazine through a nozzle. Here, the degradation of hydrazine is performed at a high temperature of 600 to 900° C., and generates rapid high-temperature thermal impact and high pressure when a high-pressure hydrazine liquid is sprayed on a surface of a catalyst and degraded. Due to the high temperature and pressure, the wearing out of the catalyst is stimulated, and the catalyst is lost, thereby continuously reducing an activity of the degradation of hydrazine.
The iridium catalyst for the degradation of hydrazine is charged in the thruster of the spacecraft, and should be used for 10 or more years when necessary. Accordingly, a crushing intensity characteristic of the catalyst is necessarily considered in manufacture of the catalyst. However, since the high temperature and pressure generated during the degradation of hydrazine cannot be tolerated only by a metal catalyst such as iridium, a catalyst for a spacecraft thruster is impregnated into a carrier. As such a carrier, generally, an alumina carrier is used.
A conventional alumina carrier is manufactured by calcining a raw material for alumina, aluminum hydroxide, through thermal treatment, molding the calcined product using an organic or inorganic binder, and crushing and wearing the molded product with a ball mill. An iridium metal salt is impregnated into the alumina carrier manufactured as described above to be used as a catalyst for a thruster. In a thruster using hydrazine as a propellant, the catalyst such as iridium is a main component, and an alumina carrier controlled in micropore characteristics is essential to the development and mass-production of such a catalyst.
However, the catalyst carrier for a thruster according to the prior art has the following problems:
The catalyst carrier for a thruster may have a continuous micropore size distribution of 1 to 10,000 nm. However, the conventional widely-used alumina carrier is composed of small micropores having a size of 1 to 10 nm even when the crushing and wearing processes are performed with a ball mill.
Accordingly, the catalyst carrier according to the prior art is decreased in a diffusion characteristic of a gas and a liquid and efficiency of the degradation of hydrazine, and thus it is difficult to control the pressure generated during the degradation of hydrazine. Particularly, due to failure at controlling the high pressure, the catalyst is crushed and worn out, and thus its lifespan is reduced. That is, a technical means for controlling the micropore size and distribution of the catalyst carrier for a thruster according to the prior art cannot be found, and thus the catalyst is crushed and worn out due to the high pressure generated during the degradation of hydrazine, thereby reducing the lifespan of the catalyst, that is, a lifespan of the thruster.